1. Field of Invention
The present invention relates to new fiber blends combining at least one high performance fiber with one or more other fibers in an intimate blend, providing combinations of properties previously unachievable.
2. Discussion of the Background
There are many methods currently present for making fiber blends. However, due to difficulties in processing high performance fibers (such as aramid, glass, or extended chain polyethylene) alongside conventional thermoplastic fibers (such as polyester, nylon, etc), various approaches have been developed to arrive at yarns containing both the high performance fibers and non-high performance fibers. These include such methods as the preparation of composite yarns having a core, around which are wrapped one or more layers/sheaths of yarn. Examples of such composite yarns are provided, for example in U.S. Pat. Nos. 4,777,789; 5,177,948; 5,628,172; 5,845,476; 6,351,932; 6,363,703 and 6,367,290.
Alternative processes used to manufacture these types of composite materials include weaving reinforcing fibers (carbon, aramide, or glass) in multifilament form alternately with multifilaments of thermoplastic matrix fibers. This manufacturing technique has numerous drawbacks, including: poor wettability, a large open-space ratio, and delamination of the reinforcing fibers.
Another technique consists of commingling the multifilaments of reinforcing fibers with the multifilaments of thermoplastic fibers. However, this technique is limited in the ability to use shorter staple length reinforcing fibers, without the need for cutting operations in the preparation of the cut reinforcing fibers. Because of this drawback, it is difficult to obtain the desired feel of the final product combined with the desired strength characteristics given by high performance fibers.
These techniques all have substantial drawbacks in several areas, not the least of which is the cost of making the yarn and difficulties in weaving or braiding.
U.S. Pat. No. 5,910,361 teaches an intimate mixture of reinforcing fibers and thermoplastic matrix fibers formed by a cracking process, wherein the fibers are arranged such that the filaments are all parallel, and must be held together by wrapping a filament of thermoplastic fiber around the assembled mixture of parallel fibers. While this produces a high modulus product, the difficulty involved in ensuring the parallel arrangement of the mixed fibers creates, among other things, added production costs.